Pretty much a zombie story at first (28 Days Later infected even), typical world ends and survivors keep surviving, the way the story goes is that it becomes increasingly absurd that you just have to laugh yet just the sight of it would be incredibly creepy. The plot starts from day 1 and literally everyone disappears, the main character is searching for other people alive which he does eventually after a few days, those he comes into contact with also don't know where everyone disappeared and they start to survive together trying to understand what just happened about where everyone went, days or weeks later, the remaining human population came back and were perceived by the survivors that they were infected with something. As time goes by (days, weeks, months and years), the "infected" quickly start having abnormalities. The infected are not really infected by anything. No alien parasite, no virus, no fungal epidemic, no vampires, no bio-weapon no nothing, they just exist. They just happened and as the title suggests, I don't want to answer why the infected are becoming like this or their true origins. I want to focus on the survivors on how the deal with such creature that constantly comes out with something new, dealing with the fact that these things even exist, it looks human but it isn't human. It's not a story of humans are the real monsters, it's really a story of how one can fight something that defies physics, the idea of something that comes back even more dangerous and unpredictable and how maddening/troublesome it is to fight just one. Would you prefer to discover why every human disappeared one day and only pockets of humans were left alone, what these creatures are and where they came from? I feel it would ruin the suspense, each encounter with the infected will always be different. I find it really unrealistic for a simple survivor to go on a journey and find out the origins of such.
There is never a need to understand the why behind something in a story either in film or fiction or whatever. Sometimes, it's just is and the toons just have to deal with it either way. Kinda like magic systems in certain books. Some offer little to no explanation and are very interesting/suspenseful because you know the bad guys can mess shit up like no tomorrow and there's squat the MC can do about it. Some are rather elaborate and really immerse you in a fantastic world. If there is no need to know the origins and you don't want to, don't include it. If anything, readers will keep on reading wanting to find out why and at the end go "huh..." in a good way.
Just a quick and unrelated question. If you were alone in an empty city with a few friends, would would any minor tremblings or vibrations be felt if thousands of people were running towards your position from a distance?
You'd hear it if anything, without cars and machines running, sound would carry quite well in a city. Trembling itself is possible since streets are rather hollow due to sewers... I'm just guessing from the little I know.
Zombies have been done to death. Pun intended but yeah.. Remember the plot holes, people will go like "Why does everyone dissapear but not the protagonist?" or "How can he not find people in days?" (assuming he lives in a huge city, and if the people haven't gone to a specific place it seems highly unlikely. And why would all people vanish except for a few? And then these zombies would run back in a group of thousands? Then it would be logical to find out where they all went, but I don't think you've thought it through.. Well, to your question, if the main purpose is to surivve then a few mysteries should be given, they don't have to be answered, but you'll have them to make the reader question what truly happened. It sounds like you have a lot of plotholes and very unrealistic way of everything happening, and you should really think that through before you think about whether there should be mysteries or not. That depends a lot on the reader, think about your targeted audience.
Plot holes differ from unanswered questions. I can handle and unresolved ending, sometimes it's enjoyable. Plot holes, on the other hand, one can only overlook so many of them. It has intrigued me recently however, why some incredulous plots don't bother me and others make me stop reading the book. I've been trying to pick out the differences but have yet to identify them.
Resolve something personal for the hero, some dilemma he has to overcome. As long the reader feels some things have been resolved, they won't care so much that other things remain a mystery as that's life anyway.
I think you have to know it yourself, otherwise it'll be difficult (but not impossible) to keep things consistent. I don't think you need to explain everything though. However, what happened seems to be the biggest question in your story, so I'm not sure why you wouldn't offer some kind of an explanation even if it's not detailed, unless you don't know it yourself either... Look at it this way: someone has to survive, and it so happens the author picks the pov of one of the survivors.
It'd be a terrible book if every human would die. There'd be no uplifting values and morals shown in the human spirit. Heck, there'd be no character. Terrible, terrible book.
It could be about animals, though, and how they start to work in the nuclear plants to keep stuff from overheating and exploding and contaminating everything.
All of the answers that are necessary. I guess some things are more fun when hinted at but left for the audience to speculate, though definitely not major plot elements.
